High-resolution fluorescence micro-scopy has revolutionized cell biology, most agree. But the revolution has not come without sacrifice. The enabling equipment--excitation sources, optics, and photodetection hardware--is expensive, and the necessary fluorescent dyes and proteins are relatively photo-unstable. Moreover, because of overlapping absorption and emission profiles, traditional fluorescent markers support only limited multiplexing; that is, researchers can stain cells for only three or four proteins at once.
Recent evidence, however, suggests change is afoot in the form of fluorescent semiconductor nanocrystals or "quantum dots." Containing several hundred to a few thousand atoms, quantum dots exhibit several desirable properties, from a biological applications standpoint. They are highly photostable, fluorescing for hours without photobleaching. Also, they are tunable, the emission spectrum depending on the crystals' diameter. With narrow emission profiles and broad excitation profiles, the dots provide for high levels of multiplexing, yet all can be excited using a single light source.
QUANTUM ROADBLOCKS ...
